HISTOLOGY OF
 MUSCLE TISSUE
 LIGAMENT
 BONE
BY
BAALA SHARMMA
SCHOOL OF PHYSIOTHERAPY
AIMST UNIVERSITY
1
Muscle tissue
 Muscle tissue made up of basic cell called myocytes.
 Myocytes elongated in one direction called muscle fibres.
 Some fibres made up several myocytes joint to each other – containing
multiple nuclei.
 Functional characteristics:
o Contractility - Shortening - generates pulling force
o Excitability - ability to respond to a stimulus, which may be
delivered from a motor neuron or a hormone.
o Extensibility - ability of a muscle to be stretched with contraction
of an opposing muscle or passively.
o Elasticity - ability to recoil / bounce back to the muscle's original
length after being stretched.
 Functions:
o Movement
o Joint stabilization & protection
o Maintenance of posture
o Heat generation
Histology of Muscle tissues
 Classified into three types according to
their structure and function:
o Smooth muscle
o Non-striated, involuntary
o Skeletal muscle
o Striated, voluntary.
o Cardiac muscle
o Striated, involuntary.
Structure of striated muscle
 Skeletal and cardiac muscle cells are called striated muscles.
 Striations - an alternating series of bands - basic contractile
unit called sacromere.
 In all types of muscle, contraction is caused by the
movement of myosin and actin filaments.
 The terms muscle cell and muscle fiber are synonymous.





Striations of muscle fiber
Under high power - alternating dark & light bands are seen.
Dark and light bands are intersected by lines.
A band contains light zone – H zone
I band bisected by dark lines – Z lines
The part between two Z lines is called – sarcomere
Structure of striated muscle
Structure of striated muscle
During contraction:

A band - remains constant

I band - shortens
Smooth muscle
 Present in wall of GIT, urinary organs, genital tracts, respiratory tubes,
wall of blood vessels, reproductive organs and glands.
 Smooth muscle arranged in bundles.
 Thick segment of one fiber lies opposite thin segment of adjacent fiber.
 Cells are connected by fusion of adjacent plasma membranes of cells.
 Slow sustain contraction.
Structure of smooth muscle
The cells are spindle-shaped (fusiform).
Nucleus is present in the thick segment – single, centrally placed.
No striations - the uniform, nonstriated appearance gives the
name smooth muscle.
Contain actin & myosin filaments.
Lack of sarcomeres.
Thick segment of one fiber lies opposite thin segment of
adjacent fiber.
Under involuntary control.
Longitudinal Section:
In relaxed smooth muscle, the nuclei are elongated with
rounded ends.
When contracted, the nuclei spiral, kink, or twist.
The cytoplasm is pink, non-striated and with little detail.
Smooth muscle
Structure of smooth muscle
Skeletal muscle
 Attachment:
o Direct - attachments so short that muscle appears to attach directly
to bone
o Indirect - connective tissue extends well beyond the muscle - tendon
and aponeurosis.
 Has ability to contract and cause movement.
 The origin and insertion may switch depending on body position and
movement produce.
Coverings :
 Epimysium - invests entire muscle / dense connective tissue that
surrounds the entire muscle and sends septa to cover fasciculi.
 Perimysium -connective tissue that surrounds a group of muscle cells to
form a fascicle – sends septa to cover muscle fibers.
 Endomysium - thin layer of connective tissue that surrounds each muscle
cell and invests muscle fibers.
o Capillaries - a rich blood supply travels through the endomysium.
o The capillaries occur at the corners of the muscle cells.
Skeletal muscle
Structure of Skeletal muscle
 Skeletal muscle fibers are:
o Long cylindrical-shaped cells.
o Multinucleated and peripherally located nuclei.
o Striated - cytoplasm filled with contractile filaments.
o Under voluntary control.
 The cytoplasm of muscle cells (fibers) are filled with tightly
packed myofibrils that extend the entire length of the cell.
 Myofibrils show an alternating series of striations
 In cross-section - polygonal shape cross-sections with
nuclei at the periphery.
 In longitudinal section - skeletal Muscle Cells - can vary in
length from a few millimeters to almost a meter.
Histology of skeletal muscle
Histology of skeletal muscle
With Hematoxylin and Eosin
(H & E) stain.
Appear as eosinophylic cylinders.
With multiple oval peripheral nuclei
(Seen just beneath cell membrane).
Cell membrane is called sarcolemma.
Cytoplasm consist of longitudinally running
myofibrils.
Striations of muscle fiber - under high
power, alternating dark and light bands are
seen.
Types of skeletal muscle fibers
 Skeletal muscle cells/ fibers are classified based on
contractile speed and metabolic activity.
 Slow twitch fibers (“red fibers” / type I fibres ):
o smaller muscle cells.
o specialize in long, slow contractions
o They stain darker than type II fibers.
 Fast twitch fibers (“white fibers” / type II fibres):
o large, predominantly anaerobic,
o fatigue rapidly (rely on glycogen reserves);
o most of the skeletal muscle fibers are fast.
Shapes of Skeletal Muscle
Structure of cardiac muscle








Partially resembles skeletal muscle.
Muscle fiber is short and cylindrical
They branch and anastomose.
They have single , oval centrally placed large nucleus.
Striations present.
Muscle fibers are joined by intercalated discs to form
functional network - they are the junctions of cells
membranes of cells.
The action potential travels through all cells connected
together forming a functional syncytium in which cells
function as a unit.
Under involuntary control.
Histology of cardiac muscle
Histology of Cardiac muscle
Ligament
 Ligaments are similar to tendons and fasciae.
 Ligament is the fibrous tissue that connects bones to other bones, very
strong, flexible, resistant to damage from pulling or compressing stresses.
 It contain bundles of collagen fibres orientated in a range of directions,
because bones can be moved apart in a range of directions.
 Bundles of these collagen are attached to the periosteum.
 Ligaments are viscoelastic:
o return to original shape when the tension is removed
o for a prolonged period of time may weakened - future dislocations
and eventually to osteoarthritis.
 Mechanical function:
o passively stabilize joints
o guiding the joints through their normal ROM when a tensile load is
applied.
o Some ligaments limit the joint mobility.
Capsular ligaments
part of the articular capsule surrounds synovial joints
act as mechanical reinforcements for joint stability.
Extra-capsular ligaments - It join together in harmony with the other
ligaments to provide joint stability.
Intra-capsular ligaments - less common, it provide stability but permit a far
larger range of motion e.g. cruciate ligaments of the knee.
ELBOW JOINT
Histology of Ligament
 Connective tissue proper – 2 clasifications:
o Loose (areolar) connective tissue - highly cellular with a sparse, random
arrangement of collagen fibers (and some elastic fibers).
o Dense connective tissue - collagen fibers with little ground substance
• Dense regular connective tissue- collagen fibers oriented in the
same direction
• Dense irregular connective tissue - collagen fibers woven in
multiple directions.
 Ligament are classified as Dense Regular Connective Tissue:
o contains densely packed collagen fibers arranged in parallel bundles.
o The collagen fibers is to provide tensile strength to tissues.
 The fibroblasts:
o This cells produce and maintain the extracellular matrix.
o The fibroblasts that produced the fibers reside in close proximity to the
collagen fibers and often only their flattened nuclei are visible.
o Their sparse cytoplasm is not visible largely because it blends in with
the collagen fibers.
 The crimped structure of the collagen fiber bundles permits stretching by
10–15% before failure.
Histology of Ligament
Histology of Ligament
collagen fibers
fibroblasts
Bone
 Bone is specialized connective tissues.
 Made up of matrix of 25% water, 25% protein and 50% mineral salts.
 Bone provides support and protection for the organs of the body,
attachment of muscles and organs, reservoir for calcium and
Hematopoiesis.
 It is hard and rigid because of mineralization of the extracellular matrix.
 Bone received rich vascular supply .
 The predominant, basic building block of bone is type I collagen.
 Bone tissue is classified into two types:
o Compact bone - forms a dense layer of cylindrical units, known
as osteon that are usually aligned with the long axis of the bone.
o Spongy bone (cancellous / trabecular bone) -forms a network of
anastomosing trabeculae (spicules) that form interconnecting
spaces containing bone marrow.
Bone
Body of Mandible
Histology of compact bone
 Bone is covered by periosteum, consists of
two layers:
 Outer fibrous layer
 Inner osteogenic and vascular layer
 Periosteum is firmly bound to bone by
Sharpey’s fibers.
 Endosteum: the wall of marrow cavity layer of thin connective tissue lining the
inner surface of bone facing bone marrow.
 Bone marrow: the marrow cavity and
spaces of spongy bone ( present at bone
ends) are filled by highly vascular tissues.
 Compact bone is characterized by the
presence of Haversian system ( osteon)
Histology of compact bone
Endosteum
Periosteum
Haversian system ( osteon)
The structural unit of compact bone.
Composed of 6 -12 concentric layers of mineralized matrix called concentric
lamellae - composed of collagen fibers with calcium deposits.
These concentric layers surround a central canal (Haversian canals) which
contain blood vessels and nerves .
The boundary of an osteon is the cement line.
Lacunae - small lenticular spaces present between the lamellae which
consist of osteocytes.
Canaliculi are microscopic canals between the lacunae.
Haversian canals are connected with one another and communicate with
marrow cavity through Volkmann’s canals.
Interstitial lamellae present in between osteon - belong to older bone.
Near periosteum outer circumferential lamellae are present
Near endosteum inner circumferential lamellae are present
Histology of compact bone
Osteon
Cement line.
Haversian canals
Lacunae
Concentric
lamellae
Interstitial lamellae
Canaliculi
Types of Bone Cells




Osteocyte (Mature bone cell)
Osteoblast (Bone-forming cells)
Osteoclast (Bone-destroying cells)
Osteoprogenitor cells - maintaining the osteoblast population & bone
mass. Located in the periosteum and endosteum.
Histology of Spongy Bone
•


The inner space lined by osteoblast and osteoclast called the endosteum.
No osteon
Lamellae as Trabeculae:
o Loosely organized lamellae rings with osteocytes
o No central canal.
o Osteocytes can be seen in layers in adult bone
o Branching network of bony tissue
o Strong in many directions
o Red marrow (blood forming) spaces.

Canaliculi: Connect the osteocytes.
Spongy Bone
The bone is strong, yet lightweight.
Histology of Spongy bone
Thank you